I appreciate all the help.
The 12v 850w AC is the main and largest load.
The other component we are also set on are the 8 100ah lifepo batteries. Those could make a 24v bank or 2 x 12v banks connected thru a dc/dc?
If I go for a 24v battery bank, what ga wire do I use to connect them batteries?
There are various approaches to wiring battery packs together.
The main considerations are
- Sometimes the battery bms will trip, and this requires the battery to be disconnected from the rest to re-set
- Safety - as in having things like fuses or breakers, the correct wire size, etc - and doing it in a way that you can actually buy the parts
- Battery terminal heating. You don't want all of the power from all of the batteries to be flowing through an individual terminal
- Charging / discharging reasonably evenly
- Maintenance and changes
This is the approach that I like to use. It puts each parallel string of batteries on it's own breaker, and uses a bus bar as the common power distribution point. It shows just one battery in each string, but I routinely use it as well for 24 volt systems with 2 batteries in series.
It is one of many ways to do it, but I like it for my own use.
Basically the batteries are on the left side of the diagram, and the loads / charging are on the right side.
It can be built using 2 awg wire ( good for 100 amps per feed ) and you can use a breaker up to 125 amps on each one.
Take a look at your batteries and see if 100 amps of discharge is appropriate for them.
This just shows 2 strings of batteries in parallel, but you can add as many as are needed - with your size system.
The DC - DC converter can be attached for example where a fuse block is shown.
The dual feed to the inverter is for use in 12 volt systems, for example if you were trying to feed 12 volts into a 2 000 watt inverter, it takes ~ 200 amps. With 24 volt, it only needs 100 amps, so it works just fine to use 1 string to feed it.
Some people like to add a battery terminal fuse to each battery "string" to provide cut off at that point as an additional safety measure.
What I really like about the concept is that it allows shutting off various portions of the system for testing or isolating things off in case they are not working correctly.
In theory you can just use a fuse instead of the breakers, but then imagine having the power of so many batteries feeding your system, and no way to really turn if off to hook something up or make changes ? This kind of arrangement is even fairly safe for teenagers to use.
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For the 12 volt air conditioner, 2 awg should also be very close to the requirement. On the blue sea web site, there is a calculator that you can use to double check.
circuitwizard.bluesea.com
2 awg wire is fairly easy to work with and widely available. You can just order on line the wires with terminals crimped on already - usually cheaper than you can buy the parts.
edit - that DC converter might be limited to 6 awg wire - cannot remember right now. It is in the data sheet / manual.